Self-interaction corrected electronic structure of Ti4O7, TiO2 and Ti2O3

We have studied three titanium oxides, rutile TiO2, Ti2O3, and Magnéli phase Ti4O7, using density functional theory with self-interaction corrections. We found that the ground state of the low temperature (T < 142 K) phase (or LT phase) of Ti4O7 is a new semiconducting state with antiferromagnetic coupling between two sublattices, while the high temperature (room temperature) phase (or HT phase) is a metal, in agreement with previous experiments. We have also investigated the dependence of electronic and magnetic properties of these Ti-O phases on the single empirical parameter α representing the applied self-interaction correction. We show that Pauli paramagnetism of the metallic HT-Ti4O7 is predicted using 0   , that the band gaps of small-gap LT-Ti4O7 and Ti2O3 are captured by 5 . 0   , while the band gap of wide-gap TiO2 is reproduced using 9 . 0   . The increasing value of α for increasing value of the gap is consistent with increasing ionic bonding and decreasing screening. Nevertheless, restricting α to the standard value for transition metal oxides of 0.5 is shown to be a good compromise describing reasonably well the electronic structures of these oxides. We also studied the effect of isotropic strain on Ti4O7 electronic structure, and we predict an antiferromagnetic-ferromagnetic phase transition for the LT phase under compressive strain.